I'm also a beginner but roughly explained with the thought of a student: SER mostly refers to permanent things (like your personal qualities, occupation, origin, etc.) while ESTAR is used to tell your location, or how you feel... (temporary things). For example: Estoy en la biblioteca -- I'm in the library. Soy americano -- I'm American. Anyways, check out some helpful sites on the subject, like this one: http://www.studyspanish.com/lessons/serest1.htm

Use "ser" beside of an adjetive or a profession, exemple. soy alto - i´m tall es bonito- it´s preaty estos autos son rojos- these cars are red el es doctor - he is a doctor and use "estar" something like "stand", "stay" be in a place or to point out a emotional status...example estoy en mi casa - i am in my house esta en un restaurante - he is in a restaurant estan enojados - they are angry my english is poor, but i hope can to help

here's the exact link to get the answer to "ser" versus "estar": http://spanish.about.com/cs/verbs/a/servsestar.htm

If you look under "resources" > "Spanish" you will find a recent posting of mine (in English) that briefly describes the differences.

SER - to be - use to define a subject - ex. Tu eres alto. (You are tall) ESTAR - verb showing condition , location, - ex . Yo estoy hambre (I'm hungry) condition Yo estoy en frente de la nuestra casa. - I'm in front of our house. AND MANY MORE....